The invention relates to a recording or reproduction apparatus with a mount for disc-type recording media, which mount retains the recording medium with means provided on the disc turntable.
Disc turntables with a hub penetrating through a centering hole in the recording medium in recording or reproduction apparatuses which have means for retaining the recording medium on the disc turntable have been known for a long time. Thus, as early as in DE-GM 7005274, a mount for records was proposed, which holds a record both radial outwardly and downwardly on the disc turntable. Corresponding embodiments of the known mount for records are illustrated in FIGS. 1 to 4. Individual spring elements are arranged at the periphery of the hub of the disc turntable, the record being pressed onto the disc turntable in the centering hole by the said spring elements. Balls are provided as spring elements, which balls partly project through openings at the periphery of the hub and, at the inwardly projecting part, bear resiliently on a rubber body. What is disadvantageous is that a force required to overcome the spring resistance has the same magnitude in both directions, that is to say during emplacement and removal of the recording medium, and different spring forces are generated by a rubber body on account of fatigue phenomena and environmental influences.
As an alternative, in the case of a disc turntable composed of plastic capable of being injection-molded, tongue-shaped springs are provided in radial slots at the periphery of the hub, the undercut limb end of which springs projects radial above the periphery of the hub and is at a distance from the disc turntable corresponding to the thickness of the record. During the emplacement of the record, the tongue-shaped springs spring back and then settle on the record. The recording medium can be removed only by applying a force perpendicularly to the direction of movement of the disc turntable, thereby rendering interchange-ability of the recording medium more difficult. The mount does not compensate for tolerances of the centering hole of the recording medium.
The object of the invention is to provide a recording or reproduction apparatus with a mount for disc-type recording media which enables the recording medium to be emplaced and removed with forces that are to be applied exclusively in the directions of movement yet are different, compensates for tolerances of the centering hole of the recording medium, applies a constant holding force even over a relatively long period of time, and has a small number of individual parts.
This object is achieved by means that are specified in independent claims; advantageous designs and developments are specified in dependent claims.
It is an aspect of the invention that despite a comparatively small force during the emplacement of the recording medium on the disc turntable, a large holding force is generated for the recording medium on the disc turntable and its interchangeability is nevertheless enabled using simple means.
According to the invention, a spring toothed disc for holding the recording medium on the disc turntable is arranged in a hub of the disc turntable, which hub penetrates through a centering hole in the recording medium and is designed in a pot-shaped manner, the teeth of which spring toothed disc are oriented at an angle to a plane formed by the disc turntable, the said angle preferably being other than 90 degrees. The spring toothed disc is arranged on an inner hub of the pot-shaped hub and can be used both in connection with balls and in connection with tongue-shaped pot-type springs as a spring element for holding the recording medium on the disc turntable. The teeth of the spring toothed disc are arranged in pockets of the pot-shaped hub in a manner secure against rotation and, with spring elements arranged at the periphery of the hub, exert a holding force having a plurality of different components on a recording medium on the disc turntable. The components of the force proceeding from the spring elements are determined by the angle at which the teeth of the spring toothed disc are arranged with respect to the plane formed by the disc turntable. As a result, in an advantageous manner, a force component provided for centering the recording medium on the disc turntable is generated which is not equal to the holding force and, consequently, in the direction of movement, an emplacement force is generated which is not equal to the removal and/or holding force, without a force having to be applied perpendicularly to the direction of movement or an unlocking arrangement having to be activated.
In the case of an embodiment provided with balls as a spring element, the teeth of the spring toothed disc bear, at an angle to a plane formed by the disc turntable, the said angle being other than 90 degrees, on the balls, which partly project through openings at the periphery of the hub, and thereby determine the spring force components.
In the case of an embodiment provided with tongue-shaped pot-type springs as a spring element, the teeth of the spring toothed disc likewise bear at an angle on the tongue-shaped pot-type springs and latching lugs are provided on the tongue-shaped pot-type springs, the said latching lugs furthermore having different inclination in the direction to and from he disc turntable. The force components exerted on the recording medium for the centering and holding of the recording medium on the disc turntable are additionally influenced by the inclination of these latching lugs. By virtue of the fact that the latching lugs have an inclination, which does not run parallel to a plane formed by the disc turntable, it is not necessary to unlock the recording medium with a force that has to be additionally applied perpendicularly to the direction of removal. With a force directed in the direction of removal, by way of the inclination of the latching lugs a force which enables the recording medium to be removed is exerted on the tongue-shaped pot-type springs supported on the spring toothed disc.
The spring toothed disc arranged on an inner hub of the pot-shaped hub of the disc turntable is preferably fixed by holding-down devices of a closure cover which engages in cutouts in the pot-shaped hub.
The mount for the recording medium on the disc turntable comprises a small number of individual parts, enables the emplacement and removal of the recording medium with different forces that are to be applied exclusively in the directions of movement and compensates for tolerances of the centering hole in the recording medium with a spring toothed disc. The production of the spring toothed disc from phosphor bronze or spring strip steel ensures that the mount applies a constant holding force even over a relatively long period of time.
A second embodiment is formed exclusively by pot-type springs which are arranged upright under a prestress at the periphery of the hub of the disc turntable. For this purpose, cutouts are provided in a latching disc, which forms the cover of the pot-shaped body and is anchored with latching webs in the bottom of the pot-shaped plastic body, into which cutouts engages a shoulder at that end of the pot-type spring which carries the lug. The elastic pot-type springs are initially produced with an angle with respect to the bottom of the pot-shaped body 28 that exceeds 90 degrees. During the mounting of the latching disc which forms the cover, the pot-type springs are then forced back until they latch into the cutouts, with the result that the pot-type springs have a prestress. With the prestress, a large spring force is advantageously achieved in spite of small spring excursions, which spring force, for a number of applications, is already large enough to hold and to center the recording medium on the disc turntables even without the support by the spring toothed disc. With a basic construction, it is thereby possible to produce different disc turntables that exert on the recording medium a holding and centering force, which corresponds to the respective purpose of use. The purpose of use is determined in particular by the rotational speed range in which the disc turntable is intended to be used.
The invention is explained in more detail below with reference to the drawings.